Staple blend of 3-methylbutene-1 copolymer and cellulosic fibers



March TENACITY g/d 3; 1970 w. J. POLESTAK 3,493,042

STAPLE BLEND OF S-METHYLBUTENE-l COPOLYMER AND CELLULOSIC FIBERS Filed Nov. 2. 1966 4 LEGEND:

Curve A Copolymer of 95.2 mol 3- methylbutene-l and 4.8 mol noctene -l 3 Curve 8- Copolymer of 98.5 mol 3 melhylbutene and L5 mol n -hexodecene l ELONGATION United States Patent 3,498,042 STAPLE BLEND 0F 3-METHYLBUTENE-1 COPOL- YMER AND CELLULOSIC FIBERS Walter J. Polestak, Summit, N.J., assignor to Celanese Corporation, New York, N.Y., a corporation of Delaware Filed Nov. 2, 1966, Ser. No. 591,572 Int. Cl. D01f 3/00; C08b 23/00 US. Cl. 57-140 9 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to an improved staple blend, and, more particularly, to a staple blend of 3- methylbutene-l copolymer fibers and cellulosic fibers, the resulting blend having increased strength.

The use of two or more varieties of staple fibers to create blends, and yarns and fabrics prepared therefrom, is well known in the art. Such blends have been produced to provide new and attractive fabrics having improved physical and aesthetic properties.

It has been found, however, that when 3-methylbutene- 1 copolymer fibers are blended with natural fibers such as cotton, the resulting blend is generally weaker than if 100 percent cotton is used, especially when only a minor amount, e.g., less than about 50 weight percent, of synthetic fiber is used. The weakness of the blends is due to the much greater elasticity of the 3-methylbutene-1 copolymer fibers. Hence, at low loads, the cotton is the stress-bearing member and because of its low break-elongation, generally below about 15 percent, the cotton ruptures before the 3-methylbutene-1 copolymer fibers bear any substantial proportion of the load.

Accordingly, the primary object of the present invention is to provide a staple blend having increased strength comprising cellulosic fibers and 3-methylbutene-1 copolymer fibers. Another object is to provide a staple blend of cellulosic fibers and 3-methylbutene-1 copolymer fibers, the latter having an increased load-bearing capacity at the break-elongation characteristic of the cellulosic fiber. An additional object is to provide a blended staple yarn of increased strength comprising natural or chemically regenerated or derived cellulosic fibers and 3-methylbutene- 1 copolymers fibers.

These and other objects are attained by blending cellulosic fibers with copolymer fibers comprising a major amount of combined 3-methylbutene-1 and a minor amount of another combined mono-ethylenically unsaturated hydrocarbon having a straight chain of at least 9 carbon atoms, the copolymer fibers having been formed by subjecting the copolymer to a heat treatment to increase the melt index thereof from below 7 to above 7, and thereafter melt spinning the heat treated copolymer through an orifice having a diameter of at least about 14 mil to form a copolymer fiber which is taken up at a drawdown of at least about 150. The resulting as-spun fiber, which refers to the fiber on the initial take-up roll or bobbin, is the copolymer fiber which is combined with the cellulosic fibers to form a staple blend of increased strength.

Drawdown is the ratio of the velocity of the fiber at the initial take-up roll or bobbin to the linear velocity of the fiber at the extruder orifice outlet.

For a better and more complete understanding of the present invention, its objects and advantages, reference should be had to the following description and to the accompanying drawing, which is a stress-strain graph showing the improved load-bearing properties of a S-methylbutene-l copolymer fiber produced according to the present invention and another 3-methylbutene-1 copolymer fiber.

Tenacity is a measure of the breaking strength of a fiber or yarn expressed in force per unit yarn number, usually grams per denier (g.p.d.).

With reference to the drawing, Curve A represents a characteristic knee curve whish is normally obtained with 3-methylbutene-1 homo and copolymer fibers (at 23 C.). It has been found, however, that if the proper comonomer, preheat treatment, and spinning conditions are employed, then a characteristic Curve B will be obtained which represents a departure from the knee curve. As can be seen from the drawing, the apparent yield, i.e., the first break in the curve departing from the straight line, occurs at a substantially higher stress on Curve B than on Curve A, and the lateral displacement or post yield is less severe in its nature as to Curve B.

Cellulosic fibers The cellulosic fibers with which the improved 3-methyl butene-1 copolymer fibers are to be blended include highmodulus natural or naturally-derived staple fibers such as cotton, viscose rayon, acetate rayon, and other fiber forming cellulosic derivatives. These cellulosic fibers normally have a break-elongation in the range of from about 5 to 15 percent. As can be seen from the drawing, in this range, the 3-methylbutene-1 copolymer fibers produced according to the present invention have an increased load-bearing capacity and less strain per unit stress than conventionally prepared synthetic fibers of similar composition. Hence, staple blends of the improved copolymer fibers and cellulosic-based fibers have increased strength. Normally, the 3-methylbutene-1 copolymer fibers prepared in accordance with the present invention have in the range of from about a 10 to 50 percent increase in load-bearing capacity at the break-elongation of the cellulosic fiber as compared with a conventionally prepared copolymer. fiber. More specifically, the improved copolymer fibers have a load-bearing capacity (measured at 23 C.) of at least about 1.8 g.p.d., and usually in the range of from about 2 to 4.0 g.p.d., at a strain or elongation in the range of from about 5 to 15 percent.

3-methylbutene-1 copolymer rated hydrocarbons containing a straight chain of at least i 9 carbon atoms and up to about 26 carbon atoms total. Preferably, the monoethylenically unsaturated comonomer is a straight chain alkene-l containing in the range of from about 9 to 20 carbon atoms, and more preferably from about 14 to 20 carbon atoms. Some comnomers within the foregoing class which may be used are nnonene-l, n-tetradecene-l, n-hexadecene-l, n-octadecene- 1, n-eicosene-l, n-hexeicosene-l or fractions containing mixtures of l-alkenes in which the average number of carbon atoms in the molecules is within the foregoing numerical ranges. For example, the comonomer may be a commercial fraction of straight chain 1-alkenes containing 10 to 20 carbon atoms with 'an average of 15 carbon atoms. These 3-methylbutene-1 copolymers normally have a melt index in the range of from about 0.5 to 5.0, and normally 1.

The copolymers comprise a major amount of 3-methylbutene-l and a minor amount of the comonomer. Generally, the straight chain alkene-l comonomers are used in an amount in the range of from about 0.5 to 20 mol percent, preferably 0.5 to 7.0 mol percent, of the total monomers employed in the polymerization mixture, and the final copolymer may contain in the range of from about 0.5 to 20 mol percent, preferably 0.5 to 7.0 mol percent of polymerized straight chain alkene-l, based on the total copolymer, the balance essentially being polymerized 3-methylbutene- 1.

Examples of preferred copolymers of 3-methylbutene-1 and their method of preparation are disclosed in US. application Ser. No. 399,091, filed Sept. 24, 1964 by Charles L. Smart, Dagobert E. Stuetz, and Manuel Slovinsky, the application being assigned to the Celanese Corporation of America.

Heat treatment The 3-methylbutene-l copolymer is subjected to a heat treatment to increase the melt index from a value of below 7, normally 0.5 to 5.0, to a melt index above 7. Preferably, the heat treatment is sufficient to increase the melt index to a value in the range of from about 7 to 50, and more preferably from about 10 to 25. These melt index values are determined according to the procedure set forth in ASTM Dl238-57T. (at 330 C.)

In order to obtain the above increase in melt index the 3-methylbutene-1 copolymer is heat treated in air or an inert atmosphere such as nitrogen, in any conventional type heating apparatus, at a temperature not lower than about the melting point of the copolymer or higher. Normally a temperature in the range of from about 300 to 500 C., and preferably from about 320 to 360 C. is used. The time required to achieve the desired increase in melt index is dependent upon the temperature employed in the heating zone, the higher the temperature, the lower the time. Depending on the temperature used, the time of treatment may range from about several seconds, e.g., 2 seconds, to several hours, e.g., 3 hours, preferably from about 10 to 60 minutes, and more preferably from about to minutes. For example, it normally requires about 15 minutes at a temperature of about 350 C. to increase the melt index of a typical 3-methylbutene-1 copolymer from about 1 to about 15. Atmospheric pressures are conveniently used in the heat treating Zones, but higher or lower pressures may be used if so desired.

The copolymer heating operation may be carried out in any suitable manner, for example, the copolymer may be introduced into a conventional type melt spinning apparatus and heat treated therein prior to, or essentially simultaneously with, being extruded. Preferably, the copolymer is heat treated in a separate heating zone prior to being introduced into the melt spinning apparatus. For example, the copolymer may be heat treated in a conventional extruder, the heat-treated copolymer pelletized, and the pellets thereafter introduced into the melt spinning apparatus; or the copolymer may be milled and then introduced into the melt spinning apparatus. In this manner, a more uniform heat treatment of the copolymer occurs, thereby yielding a monoor multi-filament spun product having uniform physical properties, which is of particular importance in multifilament spinning.

Melt spinning The heat-treated 3-methylbutene-l copolymer is melt spun in any conventional type melt spinning apparatus wherein the copolymer is extruded through a spinneret orifice. Generally, the spinneret orifice diameter is in the range of from about 14 to 80 mil, and preferably from about 20 to 60 mil. The ratio of the lentgh of the orifice to the diameter of the orifice is normally in the range of from about 1:1 to 20:1, and preferably from about 5:1 to 10:1.

The spinning temperature, which is normally the tem perature of the copolymer melt in the spinning apparatus, is conveniently in the range of from about 285 to 375 C., and preferably from about 320 to 360 C. While higher temperatures may be used, particularly if the copolymer heat-treatment is to be conducted essentially simultaneously with the melt spinning operation, the temperature should not be so high that the melt flow of the extruded fiber cannot be easily controlled. Extrusion pressures in the range of from about 500 to 5000 pounds per square inch will normally be sufiicient to extrude the 3-methylbutene-1 copolymer in the above temperature range after the material has been subjected to the aforementioned heat-treatment.

The copolymer may be extruded into air at room temperature, or into an atmosphere of an inert gas, for example, nitrogen, argon, steam or carbon dioxide, or into a liquid such as water, acetone or methylene chloride at a temperature low enough to set the extruded material as it emerges from the spinneret orifice. If a gas, for example, air, is used to quench the fiber, the gas may be circulated or jetted around the fiber as it emerges from the spinneret according to any of the commonly used processes. Such forced circulation results in better heat transfer and thus quicker setting of the fiber.

As the spun fiber emerges from the spinneret orifice it is taken up at a drawdown in the range of from about 150 to 8500, and preferably from about 1100 to 6000. The ability of the extruded fiber to be drawn to a high degree without breaking is governed by the heat treated copolymer melt index and spinning conditions, e.g., spinning temperature and spinneret orifice diameter. Simple experimentation is required to determine the exact drawndown range to be used with each set of conditions. Preferably, the maximum drawdown is used in each case since it has been found that as the drawdown is increased, the load bearing capacity or the fiber tenacity strength increases, i.e., within the aforementioned orifice diameter and drawdown ranges.

In order to achieve the above drawdowns a linear takeup speed, i.e., the speed of the fiber at the initial take-up bobbin or roll, is in the range of from about to 3000 meters per minute, and preferably from about 1000 to 2200 meters per minute.

The as-spun fibers or filaments on the initial take-up roll or bobbin generally have a denier in the range of from about 1 to 10. However, higher denier fibers may be obtained if so desired.

While the above description has been directed toward the production of a monofilament or fiber, multifilaments having improved tenacity or load-bearing capacity may also be obtained by using a multi-orifice spinner t.

The above 3-methylbutene-1 copolymer fibers are formed into a staple blend with a cellulosic fiber, preferably cotton. While any amount of the copolymer fibers may be blended with the natural fiber to yield a staple blend of increased strength, normally in the range of from about 3 to 50 weight percent of the blend is made up of the copolymer fibers, and preferably from about 10 to 30 weight percent, the balance normally being cellulosic fibers. If desired, different 3-methylbutene-l copolymer fibers of the present invention may be used in the blend. In addition, other fibers both natural and synthetic, and of higher or lower modulus such as nylon and wool, respectively, may be used in the staple blends, for example, for aesthetic properties.

The 3-methylbutene-l copolymer fibers may be formed into staple fibers and blended with the cellulosic staple fibers to form staple blends or blended staple yarns by any of the commonly used methods well known to those skilled in the art. The resulting blended staple yarn may be fashioned into wearing apparel having improved wear resistance.

The invention is additionally illustrated by the following examples.

In each of the following runs of Examples I and II the an inert atmosphere at a temperature not lower than polymer or copolymer was formed into a rod, and the rod about the melting point of the copolymer to increase melt spun in a micromelt constant pressure extruder, the melt index of the copolymer from below 7 to above actuated by a hydraulic air cylinder. Samples of the 7, melt spinning the heat-treated copolymer through an resulting as-spun fiber were collected during the spinning orifice having a diameter of at least about 14 mil to runs and stress-strain values were obtained using an 5 form a fiber, and taking up the fiber at a drawdown of Instron testing machine at a temperature of 23 C., at least about 150. relative humidity of 65 percent, gauge length of 3 /3 2. The staple blend of claim 1 wherein the monoinches, and a rate of elongation of 2.0 inches/minute. ethylenically unsaturated hydrocarbon is a straight chain alkene-l containing in the range of from about 9 to 20 Example I 10 carbon atoms per molecule. The following Table I compares the tenacity or load- 3. The staple blend of claim 1 wherein said copolymer bearing capacity (stress) in g.p.d. of the various polymer fibers have been formed by heating a 3-methylbutene-1 fibers at 5 percent and percent elongation or strain, copolymer comprising from about 80 to 99.5 mol perwhich is the normal break-elongation range of the cel- 15 cent 3-methylbutene-l and in the range of from about lulosic fibers. 0.5 to mol percent of a straight chain alkene-l con- TABLE I Spinning conditions Load-bearing capacity (g.p.d) Run Preheating Ml. Orifice Temp., Drawdown elongation diarn., mil C.

1 3-methylbutene-l homopolymer, M.I.=1 1 hr., 320 C 15 40 340 620 1. 4 2 2 Oopolymer, 3-methylbutene-1, 95.2 mol per- M hr., 350 C 15 20 350 2,280 1.3 1.8

cent and n-octene-l, 4.8 mol percent, M.I.= 1.5. 3 Copolymer, 3-methylbutene-1, 98.5 mol per- 1 hr., 320 C 15 40 340 4, 700 1.8 3.15

1ri/elnlt ang n-hexadecene-l, 1.5 mol percent,

Refers to the melt index of the polymer or copolymer after preheating. As can be seen from Table I, the 3-methylbutene-1 taining from about 14 to 20 carbon atoms per molecule copolymer fiber produced according to the present inunder conditions sufficient to increase the melt index vention (Run 3) has an increased load-bearing capacity thereof from about 0.5 to 5.0 to a value in the range at the 5 percent and 15 percent elongation. When blended of from about 7 to 50, melt spinning the heat-treated cowith cotton to form staple blends containing 30 percent polymer through an orifice having a diameter in the by weight of synthetic copolymer fiber, the blend formed range of from about 14 to 80 to form a fiber, and taking from the copolymer obtained in Run 3 substantially up the fiber at a drawdown in the range of from about outperforms blends using copolymer fibers such as 150 to 8500. those produced in Runs 1 and 2. 4. The staple blend of claim 3 wherein the cellulosic fibers are cotton. Examp 16 II 5. The staple blend of claim 3 wherein the straight The following Table II illustrates the effect of drawchain alkene-l comonomer is n-hexadecene-l. down on the load-bearing capacity. In Run 1 below a 6. An improved blended staple yarn comprising a low drawdown was used, while in Run 2 no preheating major proportion of cotton fibers and a minor proporwas employed. Run 3 includes both preheating and a tion of fibers of a copolymer, said copolymer consisting high drawdown. of from about 80 to 99.5 mol percent of 3-methylbutene-1 TABLE II Spinning conditions Load-bearing capacity (g.p.d) Run Preheatmg Ml. Orifice Temp., Drawdown elongation diarn., mil C.

1 copolymer, 3-methylbutene-1, 98.5 mol per- 1 hr., 320 C 15 40 342 1,580 1.3 1.8

finlt n-hexadecene-l, 1.5 mol percent, 2 "E16: None 20 340 2,840 1.3 1. 9

Refers to the melt index of the copolymer after preheating. The principle, preferred embodiment, and mode of and correspondingly from about 0.5 to 20 mol percent operation of the present invention have been described in of a straight chain alkene-l comonomer containing from the foregoing specification. However, it should be underabout 9 to 20 carbon atoms per alkene-l molecule, said stood that the invention which is intended to be protected copolymer fibers having been formed by heating the coherein may be practiced otherwise than as described polymer at a temperature not lower than about the without departing from the scope of the appended claims. melting point of the copolymer to increase the melt Iclairn: index from about 0.5 to 5.0 to a value in the range of 1. A staple blend of increased strength comprising from about 10 to 25, melt spinning the heated copolymer cellulosic fibers and fibers of a copolymer, the copolythrough an orifice having a diameter in the range of mer fibers comprising a major amount of 3-methyl- 5 from about 20 to 60 mil to form a fiber which is taken butene-l and a minor amount of another monoethylup at a drawdown in the range of from about 1100 to enically unsaturated hydrocarbon having a straight chain 6000, the copolymer fibers in the blended yarn being of at least 9 carbon atoms, the copolymer fibers of the characterized by having a load-bearing capacity of at blend being characterized by having a load-bearing caleast about 1.8 g.p.d. at 23 C. and at the break-elongapacity of at least about 1.8 g.p.d. at 23 C. and at the tion characteristic of the cotton fibers.

break-elongation characteristic of the cellulosic fibers, 7. The blended staple yarn of claim 6 wherein the said copolymer fibers having been formed by heating a copolymer fibers are characterized by having a load- 3-rnethylbutene-1 copolymer comprising a major amount bearing capacity in the range of from about 2 to 4 g.p.d. of 3-methylbutene-l and a minor amount of another at 23 C. and at the break-elongation characteristic of monoethylenioally unsaturated hydrocarbon in air or the cotton fibers.

7 8 8. The blended staple yarn of claim 7 wherein the FOREIGN PATENTS blend comprises in the range of from about 3 to 50 849,090 9/1960 Great Britain weightpercentwpolymer fibers- 999,727 7/1965 Great Britain.

9. The blended staple yarn of claim 7 wherein the blend comprises 1n the range of from about 10 to 30 5 WILLIAM H SHORTPIimary Examiner Weight percent copolymer fibers.

E. NIELSEN, Assistant Examiner References Cited UNITED STATES PATENTS US. Cl. X.R.

3,010,949 11/1961 Price 26088.2 10 2 17 4 93 7; 2 4 17 3,146,575 9/1964 Lund et a1. 57140 3,316,226 4/1967 Clark 260-882 

